The 5 Most Important Synastry Aspects for Marriage
When people consult astrologers about romantic relationships, most want to know whether the connection can grow into something long-term and meaningful. The underlying question is, "What kind of impact will I have on the other person?" While nothing can guarantee the outcome, I believe there are five key indicators that point to the potential for a serious partnership. Not all five need to be present, but the more of them there are, the stronger the bond tends to be.
Aspects Between the Ruling Planets
The Ascendant describes how a person engages with the outside world. The Ascendant’s ruling planet (the ruler) reflects the style of that engagement, and the relationship between two people’s rulers acts as the hook that draws them together. For example, if Jason has a Cancer Ascendant and Patty has a Libra Ascendant, and Jason’s Moon (ruler of Cancer) forms an aspect with Patty’s Venus (ruler of Libra), there will be chemistry between them.
Harmonious aspects (such as conjunctions, trines, and sextiles) may suggest that Jason’s emotionally rich way of expressing himself is well received by Patty, and that her first impression of him is charming and attractive. Challenging aspects (like squares or oppositions) may indicate that Patty finds Jason somewhat private or withdrawn yet intriguing, while Jason may be intimidated by Patty’s social ease but also fascinated. Depending on other factors in their synastry, they may be able to work through the tension, or they may not—but they will notice each other and want to learn more. If Jason’s Moon and Patty’s Venus don’t form aspects but fall in each other’s signs (that is, Jason’s Moon in Libra and Patty’s Venus in Cancer), this still matters because there is a connection between the two rulers, known as mutual reception.
Consider another example: Lauren’s ruling planet is at 1 degree Aquarius, while Tom’s ruling planet is at 27 degrees Aquarius. They are too far apart to form a conjunction, but they are in the same sign. Does this count as a connection? Absolutely. Sharing a sign gives them common ground. In all these scenarios, the two rulers can communicate smoothly, providing the spark needed to initiate a relationship. Once that spark is lit, the relationship’s potential depends on how their other aspects interact.
Connection with the Sun
The Sun represents self-awareness and identity. If Patty has planets that form aspects with Jason’s Sun, his sense of self is invested in the relationship. For instance, if Patty’s Pluto is conjunct Jason’s Sun, he may feel that Patty is forcefully reshaping or controlling his identity. However, if Jason has no planets forming aspects with Patty’s Sun, she may feel that he doesn’t affect her sense of self. While this isn’t necessarily a dealbreaker, it can create an imbalance.
What if Jason’s Moon squares Patty’s Sun? His emotional responses may conflict with her self-expression (she might see him as overly sensitive), yet he will still have an impact on her identity. Depending on her Sun sign, the friction between his feelings and her ego may be both stimulating and frustrating. Ultimately, both parties can encounter each other’s essence. So, what else influences others in this way?
Planets in Water Houses
The windows of emotional expression in a natal chart are the houses associated with the water signs: the fourth (Cancer), eighth (Scorpio), and twelfth (Pisces). If Jason has two or more planets in Patty’s fourth house, he will stir up her early memories. Depending on which planets are involved, he may remind Patty of her father. If her relationship with her father was positive, Jason’s presence may feel safe and comforting. However, if her father was abusive, Jason could trigger a very different reaction—even if he is otherwise the best partner she has ever met.
What if Jason’s planets fall into her eighth house? He may awaken deep-seated insecurities and issues around intimacy. How these are handled will depend on other factors in the chart. Patty may feel physically repelled by Jason or become intensely fixated on him. Being around Jason could activate issues with control, and she may need therapy to navigate them. The key is that Jason’s influence on her eighth house can catalyze significant changes in her (assuming she doesn’t fear him and is willing to engage). Note that while both parties may have some influence, the one receiving the planetary energy is usually more affected.
As mentioned in a previous article, if someone’s planets fall into another person’s twelfth house, they can trigger subconscious fears and release deep creativity or spiritual power. One commonality among water houses is their subjectivity; if a water house is activated, its owner may find it difficult to step back and remain purely rational.
That said, mutuality matters. As we just saw, Jason has a significant influence on Patty. What if she has no planets in his water houses? If they break up six months later, Patty will likely be devastated because the relationship is deeply important to her, whereas Jason—though he finds the relationship interesting and feels bad about hurting Patty—can detach more quickly. So, what carries even more weight than this?
Conjunction with the IC
Building on the water houses, the Imum Coeli (IC), or cusp of the fourth house, is the root of the natal chart. If the fourth house represents childhood and family, then the IC concentrates that energy. Any aspect to the IC will register, but conjunctions are the strongest, especially once a close relationship has been established. If Tom’s Jupiter is conjunct Lauren’s IC, he will have a positive, expansive influence on her. She will feel comfortable discussing her childhood with him and may even invite him into her past, looking to him as a mentor in family matters. He may also amplify some of her issues—such as weight concerns, eating disorders, or fear of abandonment—but if she is willing to talk to him, he will be understanding and supportive.
What if Tom’s Uranus is conjunct her IC? He may point out those issues bluntly (and reveal some she isn’t even aware of), which could either delight or unsettle Lauren. His background is very different from hers, yet he brings a refreshing sense of novelty. She may not feel entirely comfortable, but she cannot be indifferent to him. Returning to Jason and Patty, if his planets not only fall into her fourth house but also exactly conjunct her IC, then the themes he raises around her father and childhood will be magnified. These close contacts can have a profound impact on a person—but what can keep two people bonded in the long term?
Saturn's Connection with Personal Planets or Angles
Despite the strong attraction and deep feelings, Jason and Patty ultimately do not end up together, while Lauren and Tom grow closer. Why is that? Because there is a significant Saturn connection between Lauren and Tom. Without such a connection, couples often lack a reason to commit to each other. The most powerful connections are with each other’s personal planets (Sun, Moon, Mercury, Venus, Mars) or angles (first, fourth, seventh, and tenth houses). Connections between Saturn and the outer or social planets (Jupiter, Saturn, Uranus, Neptune, Pluto) can also be felt but are less personal.
Tom’s Saturn forms a trine with Lauren’s Moon. He feels a sense of responsibility for her emotional needs, and she feels she can rely on him. If Lauren’s Saturn also aspects Tom’s personal planets, even better (though not necessary), as this would mean the responsibility is mutual. Now suppose her Saturn squares his Mars. She may take an authoritative stance with him and earn his respect, but he may feel restricted. Although this is a challenging aspect, it can add grit and staying power to the relationship. Additionally, if Lauren’s Saturn is conjunct Tom’s Midheaven (the cusp of the tenth house), she may feel responsible for his career and public image (she may even be his superior). This connection may not be romantic, but it creates accountability in their lives. It gives them reasons to stay together long term and provides a foundation on which emotional or sexual connections can develop. If her Saturn also forms a trine with his Descendant (the cusp of the seventh house), she will be a loyal and reliable partner. These aspects may not be flashy or exciting, but without them, a relationship can struggle to endure.
Now you can see how attraction, influence, and stability manifest between two people. Clearly, this is not exhaustive—many other factors can shape a romantic relationship—but these are the five I consider most important. It is quite rare for a long-term, meaningful relationship to lack all of these.